This invention deals generally with mechanical clamping devices for mounting electronic circuit boards within a chassis, but it is suitable in any other situation which requires a clamping device with excellent heat transfer capability. It is common to use a chassis that has parallel guide channels so that individual circuit boards can slide into the channels and be connected to the appropriate electric connectors when located in the channels. It is therefore necessary to clamp the circuit boards in place to prevent disturbing the electrical connections, and the almost universal device for mechanical clamping is known as the wedgelock clamp.
The main benefit of a wedgelock clamp is that it provides a consistent clamp force along its entire length while only requiring physical access from one end. The clamp is typically loosened and tightened by means of a hex head machine screw. A typical chassis receptacle for a circuit board has channels at the top and bottom of the receptacle. The circuit card assembly is comprised of a circuit board (often mounted to a heat spreader) with wedge lock clamps attached to its face near the top and bottom edges. The assembly is then slid into the chassis channels, and the clamps are tightened. The benefits of the wedgelock style clamp that make it appealing to designers is that it is lightweight, simple and easy to manufacture and assemble.
Another requirement for any circuit board clamp is to transfer the heat generated by the circuit board components to a heat sink for disposal. However, a problem with most of the conventional clamps is that the moveable mating parts provide poor heat transfer pathways for heat to move to the receptacle to which the circuit board is mated. Since the clamps are typically used to mount circuit boards which carry sensitive heat generating components, there is almost always a need to improve heat transfer from the circuit board to the device into which it is mounted. This is the only point of physical contact with the circuit board assembly, and it is therefore the logical source of heat transfer. Often the clamps are connected to heat spreaders which collect heat from the electronic components and are used to help with thermal management of the system. As the heat is conducted from the component to the heat sink, large temperature gradients occur at the circuit board clamp location, because the conductive surface contact area is dramatically reduced due to the separation of the moveable parts which interconnect the circuit board and the receptacle into which it is being installed. As electronic assemblies in general progress and the heat transfer requirements of edge cooled circuit boards increase, this restriction in heat transfer at the clamp will become more signficant as a weakness in the system.
The present invention overcomes the heat transfer limitation in the clamp, which is the weakest link in the heat transfer path.